Shigellosis is a world wide infection, particularly prevalent among the young in developing countries, where it is associated with severe malnutrition, and in certain groups in industrialized nations. Effective vaccines are currently not available. Understanding pathogenesis of shigellosis may allow development of specific and effective prophylactic and therapeutic measures. We have demonstrated that an exotoxin produced by various shigella species is undoubtedly a key virulence factor. In fact, it may be the proximate cause of both watery diarrhea and dysentery. In studies using an in vitro cell culture model measuring cytotoxicity, we have shown that a glycoprotein receptor involving oligomeric beta 1 yields 4 linked N-acetyl glucosamine is a determinant of sensitivity to toxin. In some situations the receptor can be blocked by a terminal, beta-galactosidase sensitive, galactose moiety. Removal of this galactose increases toxin binding. This study aims at characterizing the recptors on intestinal epithelial cells, both in proximal small bowel and colon, In order to determine this we are preparing purified toxin by affinity chromatography for isotope labeling and binding studies with isolated brush borders or with intact small or large bowel cells. These binding assays will be compared with a toxin consumption assay using cytotoxicity in HeLa cells as the measure, and with direct cytotoxic effects on HeLa monolayers.